Spark plug



K. THANET Jul)r 21, 1931.

SPARK PLUG Filed Oct. 5, 1928' w w a. z 4, M w I I 1// r l/ l/ 0 e w f fw f 2 aktorami* Patented July 21, 1931 PATENT OFFICE mam' 17mm, or LosANGELES, cALu'onm SPRK PUG Application flled October 5, 1928. Serial Ho.310,528.

My invention relates to ignition devices, and particularly to sparkplugs.: and it has for its object the production of an improved sparkplug' adapted to all types of internal combustion engmes, especiallythose of unusually high compression and of the air cooled type.

. To operate with efliciency in such engines, a spark plug must beperfectly gas tight in all its parts, especially and. high pressures geerated when full charge is supplied at awide open throttle under heavyloads. The insulator must retain its original dielectric strength at thehighest Working temperatures, or the relatively high current whichisvitally needed to completely ignite the present day dense fuels, willbe diverted away from the spark gap, through leakage, and insufiicientheat from a` weak spark will cause incomplete combustion with great lossof etficiency. There are two types of spark plug in general use, viz:the open end type, and the so-called baflied type. r1`he open end typeis the most popular, being the least expensive, with an unobstructedheat path which in operation must be permitted Ito become suificientlyhot to convert the impinging mass of motor fuel and oil into gas. Thusit will remain clean, but if allowed to 4 5'0 overheatthe tip becomesincandescent and pre-ignit/ion will result. Accordingly, standard sparkplugs are made with many Variations in the heat path length and theshoulder positionof the insulator or core.J The 5 lower the shoulder inthe shell the more quickly is the heat permitted to escape through thethread section of the shell which is threaded into a metal boss in thecylinder and usually surrounded by the circulating VCooling water. Ifthe, heat path isvshort, and the shoulder is lower than .the shell, thenthe heat escapes too quickly, with the result that vthe heat path doesnot operate at high enough .temperature but merely distills ofl` thelightr er fractions of the gasoline vapor, leaving the carbon attachedto itself. With such operation, surface shortage occurs, i' withconsequent missing of the engine.

Two conditions exist today'which are, especially difi'ic'ult to meetforthe proper opder the high heatl ;eration of sark plugs. One is thegradually lncreasing t. u. content of the cracked gasolines on themarket, which has risen in seven years from 18,000 B. t. ufs per poundin the old straight run fuels, to nearly 21,000 B. t., nfs in themidwest fuels. None of these new fuels are as volatile or as easilyvaporized or as readily ignited as the old type fuels, and they all burnat considerable. higher temperatures. Added to this, many American coengine manufacturers have adopted the European system of highcompression, which is becoming common. The result is still hi hertemperature deyelopments, and hig er working pressures, which make itmore difficult to operate with the old type of plug. ln these lug's, thesteel shell with its expansion co-e cient `Very much higher than that ofthe porcelain core, simply runs away 'from its seat, and leakage of theburning gases increases the'core temperature to a point where itsdielectric strength is so badly broken down that it becomes acomparatively good electrical conductcr and so much current is shortedout that incomplete combustion is the rule.

The second type of plug I may call the bafiefa type. Examples of thistype are found in the following U. S. Letters Patent among others:Tidmarsh, No. 1,008,219, Nov. 7, 1911; OlGara, No. 1,286,074, Nov. 26,1918; Colby, No; 1,374,281, Apr. 12, 1921; Brewster, No. 1,390,014,Sept. 6, 1921; Margolin, No. 1397321, Nov. 15, 1921; Aschinger, No.1',4=19,197, June 13, 1922; Pethoud, No. 8? No. 1,450,987, Apr. 10,1923; Rasmussen, No. 1,497,985, June 17,'1924.

lt will be noted that in all of the patents cited, the bafie or bafiles,and especially those attached to the central stem, are set low down andadjacent to the opening in the end of the shell. Wherever the baflie isattached to the lower end of the central'electrode, it causespreignition at wide 'opened throttle combustions, for there isnoprovision to carry off the' heat accumulated in a relatively largebafile, or in other words there is no provision of a heat gradient tocarry the heat quickly enough to the shoulder and there dissipate w itthrough the shell into the circulating water.

Furthermore, in both baflied and open ended plugs, there isins'uificient provision for maintaining the opening through theinsulator core and around the central stem gas tight. With the old plugsthev engine that is operated at low speeds generates so little heat thatthe heat paths run cold with resulting surface shortage and cutting out.In both types, the center assembly of the electrode Wire, which is about90% nickel, and which which it is integral, as for example formedthere'on by cold pressing.

4 and 5 indicate the high expansion sleeves hereinbefore referred to;These are two cylinders of exact diameter'to fit within the gland 3 withthe horizontal flange of the baflie 17 clamped between them. The mannerof their assembly willV presently be described.

The spindle 9 at its upper end is screw) threaded, and carries'a springwasher of is lightly cemented in the -core, so that its (steel,indicated by the numeral 13, 'and a lock expansion will not split thecore, may leak, and if more thorough cementing is resorted to splittingof the core invariably results,

which is generally disastrous to the engine or valves. I

In the present plug, there are six primary elementszbody, gland,insulator, spindle, a

series of defiectors or baffles, and a series of high expansion sleeves.Two'of the bafiies are carried on the gland assembly and an intermediatebafile is attached to the central spindle. All of these baffles are setup high in the chamber or heat path, the central baifle in particularbeing protected so that it cannot become. hot enough to causepreignition. Special Valved means are provided for maintaining alljpints proof against leakage, no matter what the tempera- ;ture orpressure, sothat these plugs are especially adapted to high compressionengines using modern motor fuel.

My invention is illustrated in the accompanying drawing., in which thefigure is an aial longitudinal section of my improved p Referring to thedrawing, 1 is the body or shell, which may be of any suitable metal oralloy, internally threaded at 7 to receive the assembly gland andexternally threaded at 8 for screwing` into the engine. 2 is theinsulator or core, which may be made'of a suitable cerafmic material, orof mica. It is accurately ground to form a shoulder 15'at ap'redetermined angle and .is ground at right angles to the axis of itslong'itudinal bore 20,

on both'rends, for a purpose which will be` presently described. 3indicates the assemly gland, which is of metal, with a shoulder' at 15cqbrresponding to the shoulder. of the core and ground exaetly to thesame angle.. It has an external thread enga'gingthe internal thread ofthe casing or shell at 7. 9 indicates the central spindle, which is ofalloy steel or in case'of high temperature air cooled engines isofcopper or other metal or alloy'of high thermal conductivity with a head'11 formed on it, and an electrodea buttwelded to said head, or integralwith it. 17` and 19 indicate annular bafiles shown in section, both ofcopper or other suitable material. 18 'indicates a central baflle whichnut 14. Electrical connection from the dry or ungrounded side of thespark coil may be by the usual nut or nuts on the threaded end of thespindle, outside of nut 14, or any appropriate form of clamp orconnector may be used. The'spring washer 13 sets closely against theground outer face of the insulator 2, and the head 11 on the spindlesets closely to the ground inner face of the insulator, with a thinannealed copper gasket 12 interposed between the contiguous faces'.Suficient clearance is left in thebore of the insulator to permitexpansion and contraction of the spindle without oracking the insulator,and when the nut 14 is set up tightly, the respective washers restingagainst the two ground faces of the insulator and backed by the nut 14and the head 11 constitute valves which' efl'ectually prevent leakage ofthe hot gases through the insulator and around the spindle.

Assembly in turn seated upon said sleeve and then the,

spindle 9 is inserted in the insulator with its thin copper washerbetween the `head 11 and the ground face of the insulator and is held toa seat by means of the nut 14 resting against the spring washer 13,which in turn bears against the ground upper end of the insulator, theseparts thereafte'r acting also as a valve to` revent leakage.

The sleeve V5 is t en inserted, and the lower edge of the assembly glandis swaged over the edge of the sleeve 5, as shown at 6 in the dra-wings.This completes the assembly gland, with all its parts. The baflle plateor defiector 19 is then dropped into the bottom of the upper opening inthe shell 1 and the gland is screwed down upon the same by vmeans ofthread 7 the entire assembly being turnedup by means of said threads.

. Operation T he operation of my improved plug n engine 1s as follow's:Should there be an abundance of richvap'or, or oil charged va;

por working upward toward the interior of the plug, the first baflie ordeflector 19 is met land the greater quantity of said vapor is defiecteddownward or outward. Since the orifice in the defiector 19 is materiallysmaller in area than the open end of the Shell 1 in the engine, onlya'very small quantity of the Vapor or oil finds its way to the interiorof the plug. The portion which does enter however, meets the seconddefiector or bae 18 secured on the electrode end of the spindle and isalso deflected downward or out-Ward, and by this means the insulator 2being lochted considerably higher up, is never affected by the carboni-n the vapor. Further protection is afforded by the battle or defiector17, which in case oil or 'Vapor does penetrate so far, continues theaction of the two lower defiectors..

It will be noted that the method of assernbling the insulator in theassembly gland,

.forms a valve on a valve seat, at 15-16, and

'respectively Such a difference might result in opening of the valve dueto over expansion of the gland 3, and to prevent this I have made thefollowing provision: the two sleeves 4-5 are made of aluminum or alloyaluminum with a considerably higher coeficient of expansion than thebrass. Hence the expansion of these sleeves, acting between the shoulder6 of the gland '3, and the lower face of the insulator 2, tends to forcethe insulator upward and (o maintain its shoulder seated snugly againstthe ground shoulder of the gland, at 15-16. By careful. calculation,these parts can be made to proport-ionally increase the pressure on theinsulator seat 15-16, in exact ratio with the difference in expansion ofthe two dissimilar materials'mentioned, and a perfect gas tight seat isthe result at all times and under all conditions of heat and pressure.

In this connection, it should be noted that a very important part of myinvention, lies in building the defiector or battle 18 integral with andlocating it at the proper point on the electrode 9a; for whilethere havebeen spark plugs .with deflectors or bafiles attached to the lower endof the electrodes or spindles, for the purpose of keeping oil out of theinterior of the plug, none of these to my knowledge have been successfulfor the reason that being exposed, the heat absorbed by these ratherlarge masses of metal cannot be carried away quickly enough through thespindle, and as a consequence, at wide open throttle running, while themaximum temperatures are developed, they become incandescent, andpreignition invariably results. But with the bafile or defiector 18placed as shown in my plug, it is far enough away from the heat toescape this very serious fault. the bafiie 18 is located near the upperend of the electrode, approximately one-fourth of the length of theelectrode from the insulator, and it is protected by the lower baflle 19within and above which it lies. All three of my haflles 17, 18, 19, itwill be observed, lie above the middle point, or approximately themiddle point of the electrode 9a, so that approximately one-half of theheat path surrounding and above the electrodes ta-10 is clear ofobstruction, and there is no possibility of the bafile 18 becoming overheated or incandescent.

VVhat ll claini is: i

1,. A spark plug comprising the following instrumentalities: a tubularmetal shell, a tubular metal gland fitted within one end of said shell,an insulator fitte-d in the outer end of said gland so as to leaveanextended heat path within the same and the shell in length not lessthan twice its own diameter, a'mei'al spindle extending through theinsulator, an electrode secured to said spindle and extending throughsaid heat path axially of the shell to the open end thereof, an annulardefiector or baffle secured in said shell approximately midway of thelength of said heat path, surrounding said electrode with clearancebetween them, and a second annular bafie secured on said electrodebetween said first baffle and said insulator, together with a returnspark member for said electrode, at the open end of the shell.

2. The spark plug described in claiin l,

in which the second baffle plate is approximately midway between theinsulator and the first loafiie and is conical in Shape with its skirtextending downwardly and outwardly from the upper part of the electrode,

so as to cover the 'clearance opening between the first bafiie and saidelectrode, said first baflle being also approximately conical, with itssides extending inwardly and downwardly .toward the electrode, but outof contact therewith.

3. The spark plug described in claim 1,

having the insulator formed with a ground joint or the equivalent at thepoints of its engagernent with the gland, and with'equivalent gas tightjoints at the inner and enter ends Of the spindle, adapted to closetogether in the direction of and in response to pressure thereon wherebyall joints are maintained against leakage, at all temperatures andpressures.

4. rhe spark plug described in claim 1, having a third -defiector orbatlie similar to the first, with its outer edges secured in the glandabove the second bafiie, and with its Specifioally, i

inner edge Surrounding the electrode between said second bafile and thespindle head.

5. A spark plug comprising the following instrumentalities: a tubularmetal Shell, a tubular metal gland fitted therein, an insulator fittedin the upper end of said gland, So as to leave a heat path eXten-dingthrough the greater part of the length of Said Shell, its own lengthbeing not less than twiceV its daineter, a spindle extending throughSaid insulator, an electrode forming a continuation of Said spindle andextending through said heat path axially of the Shell to the outer endthereof, and a plurality ofv metal deflectors or baiiles, all Set highup in the Chamber or heatl path, one of said baffies being Seured tosaid electrode, and protected by a lower bafiie surrounding theelectrode and having a clearance therefrom of less than the diameter of,the protected baiile, so that Said bafile cannot become hot enough tocause preignition. v

6. The spark plug described in claim 5., in which the bafile attached tothe electrode is intermediate of two other baflies both surl'ounding theelectrode with an annular clearance therefrom, and having their outeredges clamped in the assembly of the gland and the 'sembly constructedof metal having a higher coeffi-cientl of expansion than that of thegland, said means acting against the lower face of .the insulator, toforce the latter up as the temperature rises, and by the difference inexpansion to compensate for expansion of the body of the gland, wherebythe valve shoulder on the insulator is maintained in close contact withits seat shoulder on the' gland.

9. A Spark plug comprising the following instrumentalities: a tubular"hell having an internal shoulder, an assembly gland fitting withinsaid'shell above Said Shoulder, an in- ,wardly turned fian'ge formed onthe outer,

end of Said gland, an insulator shouldered to fit the shoulder on thegland, and having its body extending only part Way through the -bore ofSaid gland,expansion means inserted i within the open end of the glandbelow the insulator, and means upon said gland engaging said expanslonmeans to hold the Same against Said insulator, the metal of Said glandand the metal of said expansion means having different coeffieients ofexpansion.

10. The spark plug described in claim 9, having the expansion meansformed in sections, with an annular deflector or baflie surrounding thecentral electrode and having its outeredge clamped between the Sectionsof said expansion means.-

ll. The spark plug described in claim 9. in which the gland assemblyincludes the gland itself, the insulator shouldercd to projest from theupper end thereof, expansion means inside the gland to hold theinsulator in position, and a flange on the gland swaged over on Saidexpansion means to hold the same rigidly in position.

12. A Sparlr plug comprising a Shell, an insulator Seated in said Shell,and holding means for Said insulator comprising elements havingdifferent coefiicients of expansion, adapted to exert pressureoppositely on Said insulator, and adjusted -so that said oppositepressures will always balance and maintain the joint or joints aroundlthe insulator gas tight.

13. A Spark plug comprising a Shell, an in- Sulator secured gas tight inSaid Shell, an opening through said insulator, a conducting spindlepassing through said opening, an electrode carried by said spindle, and.means on Said spindle responsive to changes in pressure Within theShell to maintain said opening through the insulator sealed gas tightunder all conditions.

14. A. spark plug comprising the following instrumentalities: a tubularShell internally Shouldered about midway of its length, an

'annular metal deflector or baffle having its e outeredges resting onsaid Shoulder, and an assembly gland screwed into the enlarged bore ofthe Shell against said baflle7 Said assembly comprising a tubular metalgland internally shouldered at one end, a shouldered insulatorprojecting from said end, with a Shoulder engaging the gland Shoulder, aspindle extending through said insulator axially with the Shell, anelectrode forming a continuation of Said spindle and extending throughthe Shell to the open end thereof, a metal expansion tube inside thegland below the insulator, means at the lower end of the gland engagingsaid expansion tube to hold itl and the insulator in position, and aprotecting baflle formed of metal integral with and projecting from theelectrode above and within the first men- 'tioned annular baflle,whereby it is protected from the heat of expansion and prevented frombecoming incandescent and causing preignition.

15. A spark plug comprising a tubular Shell, means for Securing one endof said Shell to the body of an engine. a shoulder within Said Shell,and an assembly gland together with a plurality of deflectors or battleplates. an insulator, a spindle in said insulator with mmm a contnuin-gelectrode extending thmugh said bafles, and adjustable means forsecuring said gland in the Shell `so arranged as to tune up the entireassembl of gland, Shell, nsulator and other parts m the gland and;between the gland and Shell When the adjustment is tightened.

In testimony whereof I- hereunto 'afix my signature.

THANET.

